How not to return a returntype in superclass

I got a question about an abstract class.

I'm developing an android application and wrote an abstract class which extends the AsyncTask<Void, Fragment, Fragment> class. The doInBackground method has already a body in my abstract class but I don't want to return anything here. Now my subclass that extends that abstract class should override that doInBackground method again, call super, do some work and then return a value.

So if I do not have a return statement in my abstract class Android Studio flags my method with an "Missing return statement" error. Is there a way to avoid this error message, because my subclass has a return value and so it should be no problem, should it?